I will offer a different opinion as I went with the CQ version.
The minor loss of velocity/effective range generally has a detrimental effect out past 800 yards. At that range with the M82 platform in general, unless you are shooting at humvee sized targets, the accuracy of the platform isn't going to be knocking over bowling pins at that range with either the 20 or 29" variety. On the flip side the CQ is supposedly a bit more accurate as the shorter barrel reseats with better repeatibility in the locking collar than the longer barrel version. However, that said I dont have a 29" barrel version to compare to either.
I like the fact that the CQ is a bit more compact overall (I am personally just more partial to more compact rifles be it a 10" M16 or a 20" M82), weighs a bit less than the longer barrel version, has a fully chrome lined barrel, and is duracoated so I don't have any corosion concerns.
I never really planned to shoot my M82 past 500 yards and only at civilian-esqe targets (paper, tannerite, used brake rotors, fruit, cinderblocks, old tv's, etc) so having that little extra 200+ft/sec velocity out of the longer barrel to give that extra "punch" that may be critical to harden military type targets didnt outweight the other benefits the CQ offered over the 29" inch version in it's civilian life with me. There was also the hope of slightly better accuracy as that is the biggest downfall of the M82 with its reciprocating/moving barrell assembly.
I am not a military sniper defending my unit, don't hunt with my M82, and don't have any delusions of SHTF senarios where I am humping a M82 along with my wife taking head shots ala Rambo 4.... so that pretty much puts it's in the "toy" category for me and the CQ just seemed to fit the "more fun" and "easier to deal with" attributes over the M82A1 or M107.
Long term if I find myself wanting to shoot much out past 500 yards or some sort of long range competition, I would probably aquire an M99 or AR50 and handload or purchase match ammunition to go with it.
Overall you really can't go wrong with either version as it is probably one of (if not) the most fun/exotic/powerful rifles you can purchase without a tax stamp.
James
Aust